An argument against abolition of the insanity defense

Penn Law’s Stephen J. Morse co-authored a Supreme Court amicus brief that says some form of insanity defense is required by the Constitution.


In the Supreme Court case, Kahler v. Kansas, the petitioner seeks to overturn the Kansas Supreme Court’s decision permitting abolition of the state’s insanity defense. Penn Law School Professor Stephen J. Morse, a widely respected expert on the impact of mental health on criminal responsibility, and University of Virginia School of Law Professor Richard J. Bonnie, co-authored an amicus brief on behalf of criminal law and mental health law professors arguing that the defense is legally and morally necessary and should be constitutionally required; 290 criminal law and mental health law professors signed the brief.

James Kahler shot and killed his wife, two of his three children, and his wife’s grandmother. Kahler’s expert witness testified that he had exhibited symptoms of multiple forms of mental illness, and the defense argued that, as a result, he had not made a “rational choice” to commit the murders, and thus was not legally culpable. However, under a Kansas statute passed in 1995 and previously upheld by the Kansas Supreme Court, the affirmative defense of legal insanity had been effectively abolished, and the jury was only permitted to consider a mental disease or defect to the extent it indicated “that the defendant lacked the mental state required as an element of the offense charged.” Kahler was convicted and the Kansas Supreme Court affirmed the conviction on appeal, rejecting his constitutional challenge to the statute.

Morse and Bonnie’s amicus brief addresses the question of whether the Eighth and Fourteenth Amendments permit a state to abolish the insanity defense. They argue that some form of insanity defense is required by the Constitution.

The group of law professors who signed the brief was bipartisan, says Morse, the Ferdinand Wakeman Hubbell Professor of Law, a professor of psychology and law in psychiatry, and the associate director of the Center for Neuroscience & Society. “We had ex-prosecutors, people known to be prosecutorial in orientation, and also people from the defense side, including former defense attorneys, public defenders, and academics with a defense orientation.”

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